Congestive cardiomyopathy is a form of primary myocardial dysfunction in which patients usually deteriorate progressively, with median survival estimated at two years. Its pathogenesis may be immune-mediated. Anecdotal series suggest that anti-inflammatory therapy may be beneficial. The role of endomyocardial biopsy in management of congestive cardiomyopathy remains controversial. The Congestive Cardiomyopathy Protocol is a prospective, randomized study of anti-inflammatory therapy with Prednisone and, in some cases, Cyclophosphamide. Initial evaluation of each patient includes extensive invasive and noninvasive cardiac testing, including endomyocardial biopsy. After pathological stratification, patients are assigned randomly to an anti-inflammatory treatment group or to a control group. Detailed inpatient re-evaluations are conducted periodically from three months to two years. Concomitant with the assessment of efficacy of anti-inflammatory therapy, questions being scrutinized include: (1) whether histologic and immunologic analysis of endomyocardial biopsy specimens will provide prognostic indication, (2) the natural history, (3) the incidence of cardiac inflammation in congestive cardiomyopathy, and (4) the utility of hemodynamic measurements, echocardiography, gated blood pool scanning, and other techniques in management and prognostic assessment of patients with congestive cardiomyopathy. This study represents the only randomized trial of anti-inflammatory therapy in patients with inflammatory dilated cardiomyopathy: 59 patients have been entered to date in this study which will determine whether the risks of commonly used steroid treatment are justified by beneficial results.